In general, values such as delay times of signals generated in a typical electrical touch sensor are set in the production process, so that it is impossible to adjust the set values even when the values varies due to several factors in actual use.
FIG. 1 is a block diagram showing the configuration of a conventional touch sensor, which has an input signal generation unit 10, a reference signal generation unit 20, a plurality of touch sensing signal generation units 30-1 to 30-n, and a plurality of touch signal generation units 40-1 to 40-n. 
Referring to FIG. 1, the input signal generation unit 10 generates an Alternate Current (AC) signal or a clock signal as an input signal R_Sig and applies it to the reference signal generation unit 20 and each of the touch sensing signal generation units 30-1 to 30-n. 
The reference signal generation unit 20 always delays an input signal R_Sig by a predetermined time regardless of whether a touch pad is touched with an object, thereby generating a reference signal Sig1.
The touch sensing signal generation units 30-1 to 30-n have respective touch pads PAD with which the object is touched, and generate sensing signals Sig2-1 to Sig2-n. The delay time of each sensing signal when the touch pad is touched with the object is longer than that of each sensing signal when the touch pad is not touched with the object.
Here, any object having a predetermined capacitance can be the object, and a representative example thereof is a human body capable of storing a large amount of charges.
The touch signal generation units 40-1 to 40-n sample and latch the sensing signals Sig2-1 to Sig2-n outputting from the respective touch sensing is signal generation units 30-1 to 30-n in synchronization with the reference signal Sig1. And, the touch signal generation units 40-1 to 40-n output respective touch signals S1 to Sn.
FIG. 2 is a circuit diagram showing the detailed configuration of the touch sensor of FIG. 1.
Referring to FIG. 2, the reference signal generation unit 20 is composed of a first resistor R1 and a capacitor C, each of the touch sensing signal generation units 30-1 to 30-n is composed of second resistor R2-1 to R2-n and pads, and each of the touch signal generation units 40-1 to 40-n is composed of a D flip-flop.
The first resistor R1 and the capacitor C are set such that each of the delay times between the input signal generation 10 and the D input of each flip-flop is shorter than the delay time between the input signal generation 10 and the capacitor C when the touch pad PAD is not touched with the object, and each of the delay times between the input signal generation 10 and the D input of each flip-flop is longer than the delay time between the input signal generation 10 and the CLK input of each flip-flop when the touch pad PAD is touched with the object.
The second resistors R2-1 to R2-n are set to match delay components between the input signal generation unit 10 and the respective touch pads PAD to be equal to each other. And each of the touch pad PADs acts to generate a capacitance corresponding with a capacitance of the object.
That is, a delay time of the reference signal generation unit 20 is constant regardless of whether a touch pad is touched with an object. And each delay time of the touch signal generation units 30-1 to 30-n is shorter than the reference signal generation unit 20 when each corresponding touch pad PAD is not touched with the object, but each delay time of the touch signal generation units 30-1 to 30-n is longer than the reference signal generation unit 20 when the touch pad PAD is touched with the object.
The D flip-flops 40-1 to 40-n are triggered in synchronization with the reference signal Sig1, and latch and output the sensing signals Sig2-1 to Sig2-n. 
Each touch sensing signal generation unit might have different delay when the touch pad PAD is not touched with the object. That is, product values of the resistors R2-1 to R2-n and the capacitor from the PAD could be different from each other. Here, the capacitor is mainly from line lengths between a touch pad and a touch signal generation unit. The line lengths may not be equal in actual application and the resistors R2-1 to R2-n may not be equal due to their variation. Thus, each sensing signal delay against the reference signal delay may vary for different line lengths between the touch pad and the touch signal generation unit, so that means for correcting delays to be the same in the production process are strongly demanded to realize equal sensitivity for all touch pads.
Even when such problems are solved in the production process, circumstances such as temperature, operating power supply voltage, and moisture, or set values or durability of discrete elements such as resistors or capacitors disposed within the touch sensor may vary in actual use. Consequently, delay times between the reference signal and the sensing signal may vary from the initially set value, which thus prevents the touch sensor from keeping precise sensitivity.